This specification relates to thermal management of film deposition processes, e.g., during the manufacture of solar cells and other devices.
Thin and other films can be formed on substrates using a variety of different deposition processes. Examples include physical deposition processes in which a deposition source is energized so that matter escapes from the deposition source. At least a portion of the escaped matter contacts a target substrate, de-energizes, and forms a solid film. For a variety of different reasons—including the need to maintain sufficient film purity—physical deposition processes are generally performed in a low pressure deposition environment (e.g., in an evacuated vacuum chamber).
Evaporation is one example of a physical deposition process. Evaporation sources can be energized using, e.g., a resistance or other heater or an electron beam to raise the vapor pressure of the source in the deposition environment. At least a portion of the vaporized source material condenses on a substrate and forms a solid film.
The deposition of matter at a substrate can transfer at least some of the energy that allowed the matter to escape from the deposition source to the substrate. For example, the condensation of vapor on a substrate will heat the substrate. Excessive heating can, e.g., damage microelectronic components on the substrate or melt portions of the substrate. The rate of deposition can be kept relatively low so that the rate of energy transfer from the deposition source to the substrate is also kept relatively small. However, slower rates of deposition increase processing times and decrease yield per unit time.